Dispensing and spraying apparatus and method

ABSTRACT

A method and apparatus for air stream dispensing and spraying of pulverulent material with less noise is described using means for developing two separate outward air flows from a dispensing gun. One flow is of a high velocity and the second flow is of a lower velocity. After both flows leave the gun, the lower velocity flow surrounds the high velocity flow (e.g., as concentric annular flow about a columnar flow). Pulverulent material is fed to the lower velocity flow to be entrained therewith and transferred, at least in part, downstream from the gun to the higher velocity flow and thus finely dispensed over a desired area or product.

[ Mar. 26,1974

1 1 DISPENSING AND SPRAYING APPARATUS AND METHOD [75] Inventor: William E. Shockley, Eaton, Ohio [73] Assignee: Baxter Laboratories, Inc., Morton Grove, Ill.

[22] Filed: Dec. 1, 1972 [2]] Appl. No.: 311,059

[52] US. Cl 239/8, 222/193, 239/336, 239/419, 239/422, 239/424 [51] Int. Cl B05b 7/00, BOSb 13/02 [58] Field of Search 239/336, 4193, 422, 423, 239/424, 428, 419, 810; 222/193 Primary Examiner-M. Henson Wood, Jr.

Assistant Examiner-Andres Kashnikow Attorney, Agent, or F irm*Richard G. Kinney, Samuel B. Smith,Jr.; Louis Altman [57] ABSTRACT A method and apparatus for air stream dispensing and spraying of pulverulent material with less noise is described using means for developing two separate outward air flows from a dispensing gun. One flow is of a high velocity and the second flow is of a lower velocity. After both flows leave the gun, the lower velocity flow surrounds the high velocity flow (e.g., as concentric annular flow about a columnar flow). Pulverulent material is fed to the lower velocity flow to be entrained therewith and transferred, at least in part, downstream from the gun to the higher velocity flow and thus finely dispensed over a desired area or product.

10 Claims, 7 Drawing Figures DISPENSING AND SPRAYING APPARATUS AND METHOD The present invention relates to a method and apparatus for dispensing a pulverulent material such as a talcum or other like powdery substance on a product which may be formed by dipping or otherwise coating a mold or form with a latex or plastisol solution. While apparatus of the type contemplated herein may have many uses, the description to follow specifically describes, without any intent to limit the apparatus to such use, a dispensing apparatus for powdering the inside surface of a glove formed by either of the aforementioned or other glove making techniques.

Many glove products are formed of plastic. The glove product, depending upon that use for which the glove is intended, may be formed with a relatively thin film wall throughout. It is not uncommon that the film be within the range of a few mils in thickness. A glove of this type is particularly adapted for a surgeons use. In this connection the thin film permits more finger sensitivity. However, a glove having the required thin wall thickness for the purpose described is extremely delicate and may rupture unless extreme care is taken during the donning procedure. It is, however, necessary that the glove be easily donned and the technique of donning to maintain sterility is well recognized. To assist in the technique of donning a talcum or other powder previously deposited on the inside of the glove serves to overcome resistance of the glove film to movement over the hand.

Apparatus capable of the deposition of talcum or other powder is well known in the prior art. One form of prior art apparatus comprises structure providing a path for air under pressure to flow from one end of the powder gun toward a nozzle arrangement at one end of a barrel. Within the air flow channel through the gun there is a flow constriction providing a Venturi effect. Pulverulent material is introduced into the flow within the region of the constriction. The material enters the flow due to the combined forces of gravity and the created vacuum condition at the constriction to travel in entrained fashion with the flow through the pneumatic powder gun.

Apparatus for making gloves of the type discussed above provides a conveyor of the over/under type (following generally the path of movement of a vehicle tread) which carries a plurality of molds forming an array between a pair of spaced conveyor chains. The number of molds in each array may vary from a few to as many as 12 to 16 molds, determined by the spacing between the conveyor chains.

In most prior art installations a powder gun will be disposed adjacent to each chain. Even so it has been found that a rather high pressure flow of air is required to disperse the entrained pulverulent material to each of the glove carrying molds in the array.

Certain problems arise because of this requirement. One problem concerns the inability to achieve even dispersion of pulverulent material over the surface of each glove at the pressure required for operation. A second problem is with regard to the development of an intolerable noise level because of the need of a high pressure driving air flow.

The present invention overcomes the abovedescribed problems and those disadvantages recognized in prior art apparatus for dispersing pulverulent material. The apparatus to be described below improves the manner and uniformity of dispersion of pulverulent material on each of several glove carrying forms in an array. The apparatus to be described below also reduces significantly the operation noise level through the use of a lower pressure air drive for the material to be dispersed.

According to an important aspect of the present invention, a secondary air flow is incorporated in a pneumatic powder gun. As will hereinafter be described in significant detail, the secondary air flow comprises a flow at a pressure reduced from the pressure of a primary air flow. The secondary air flow is caused to traverse the pneumatic powder gun generally in an annular form to exit the barrel in surrounding enveloping relation to the primary higher pressure air flow. Pulverulent material is introduced to the secondary flow to travel entrained therewith and as a consequence of the reduced pressure flow more even dispersion of material is achieved. Because of the enveloping relation of the secondary flow to the primary flow there is a smaller pressure of pressur between the air surrounding the primary air fiow than would otherwise be experienced. Thus, there is less noise.

There has thus been outlined in broad fashion an important feature of the present invention for the purpose of better understanding of the same through the more detailed description thereof that follows. Through reading of the more detailed description other features of the invention, forming the subject of the claims appended hereto, will become evident to those skilled in the art. Those skilled in the art will appreciate that the conception upon which this disclosure is based may be utilized readily as a basis for the design of other structures for carrying out the several purposes of the invention. It is important, therefore, that each claim be regarded as including such equivalent constructions as do not depart from the spirit and scope of the invention.

The accompanying drawings, forming a part of the present disclosure, illustrate a preferred embodiment of the invention. By these drawings,

FIG. 1 is a perspective view of the pneumatic powder gun of the present invention in an environment of use;

FIG. 2 is a top plan view of a portion of the structure of FIG. 1, certain components being sectioned or broken away to provide clearer understanding;

FIG. 3 is a view in elevation and partly in section illustrating the apparatus of FIG. 1 in more detail;

FIGS. 4 and 4a are vertical sections of the full length of the pneumatic powder gun;

FIG. 5 is a vertical section as seen along the line 5--5 in FIG. 4a; and,

FIG. 6 is a vertical section as seen along the line 6-6 in FIG. 4.

The pneumatic powder gun device 10 may be utilized in conjunction with apparatus for forming a product, such as a glove, by the technique of dipping a form into a rubber latex or plastisol solution or otherwise casting the material onto the form. Particulars of the glove making process are well known in the prior art and will not again be detailed herein. Suffice it to say that one of the many steps, particularly relating to apparatus for the formation of plastic gloves having a relatively thin wall of 2 to 5 mils thickness and, therefore, very easily ruptured during donning, may provide for the dispersion of a pulverulent material upon the glove prior to its being stripped from the form.

The material may be a talcum or other powder which in small quantity will adhere to the plastic surface. Upon stripping of the glove from the form the powdered surface becomes the inner surface of the glove. The small quantity of powder permits ease in donning of the glove with substantial reduction in the frequency of rupture.

In the preferred embodiment a pair of pneumatic powder guns are employed, one to each side of a conveyor and a travelling array of glove carrying molds. The spraying operation is carried out substantially within a hood 12 providing a lower chamber area 14 and an upper generally pyramidal shaped top closure 16. The closure terminates in a duct 18 connected to a system for ventilating the interior of the hood. In this manner large build-up in volume of the eddying powder will be prevented. The hood may be of any particular construction.

A pair of windows or apertures 20 are provided in opposed sides of the hood within the region of the chamber 14. Each aperture is of enlarged rectangular form to permit adjustment of the position of the powder gun relative to the glove carrying molds. The aperture is formed in the hood in disposition slightly above the tips of the fingers of glove carrying molds of the array so that the powder may take a general downward direction toward each glove carrying mold. More particularly, the pneumatic powder gun may be supported by a frame structure 22 in orientation that permits the barrel of the powder gun to be directed downwardly by an angle of approximately to 20. In this manner the powder gun or more particularly the spray of powder material emerging from the nozzle (illustrated by the several arrows) will be directed toward the outermost glove carrying mold. Further, the outer mold will not act as a barrier so that the powder will also pass toward the glove carrying mold disposed at the center of the array.

A hopper 24, also supported by the frame structure 22, is positioned so that an outlet 26 is immediately above a funnel 28 on the pneumatic powder gun. The manner of support may be by any convenient means. Powder in quantity sufficient for prolonged operation is carried by the hopper. The powder is dispensed in a constant flow to the powder gun as is required for adequate powdering of the product. Suitable dispensing may be achieved through a rotary sieve-like action. To this end a rotary member (not shown) may be mounted for movement on the drive shaft of pulley wheel 30. Constant speed drive may be provided by motor 32 through a belt 34.

The support 22 may be secured to the hood structure by brackets 36 at one or more locations. The structure for mounting the pneumatic gun on the support (not shown) through any conventional means adapts the pneumatic gun for adjustment relative to the travelling array of glove carrying molds thereby to assure proper orientation of the barrel of the gun both in the vertical and horizontal planes. Adjustment accommodates arrays of more or less molds and varying spacing between arrays to achieve uniform powdering of the glove carrying forms.

In the illustrated embodiment each array includes a plurality of three groups of glove carrying molds. To this end, each array includes three plates 38 supported equidistantly on a rail 40 mounted at opposite end to chain members 42 driven in the direction of the arrow by drive means (not shown). A plurality of four glove forms 44 are supported on each plate. The molds are mounted on the plate so that the plane of the mold is parallel to the line of movement and the thumb forming portion trails the finger forming portions.

A molded glove 46 including a cuff bead 48, somewhat exaggerated in dimension, may be seen in FIG. 3.

The pneumatic powder gun is also positioned such that its barrel is directed somewhat toward the line of motion of each array. To this end the nozzle may be positioned forward by an angle of approximately 10. FIGS. 2 and 3 illustrate the disclosed disposition of the barrel and depicted by the several arrows the spray of powder therefrom. The particular orientation as heretofore discussed permits powder to transcend horizon tally the distance from the barrel to the center mold of the array before being blocked by the end mold of the next array. The vertical angle of orientation permits the powder to flow in a generally downward direction to aid in further disposition as the powder thereafter moves generally upward because of the creation of eddy currents of air and entrained powder within the hood.

While the preferred embodiment may provide a plurality of three plates 38 in each array and four glove carrying molds on each plate, the array may also provide a plurality of other than three plates and other than four molds per plate. The particular construction will be limited by the available space for the conveyor system.

A line 50 connecting to a source of air (not shown) is supported by the hood. The main line provides a plurality of secondary lines 52 connected thereto and carrying at the other end a multidirectional outlet nozzle 54. Air from the nozzle serves to remove by air jet powder which may deposit upon the wrist portion of mold 44 or the plate, rail and chain 38, 40 and 42, respectively. As may be apparent there are sufficient secondary lines 52 to provide an outlet nozzle at each side of every mold.

Details of the pneumatic powder gun may be seen to advantage in FIGS. 4 and 4a. The gun includes a primary air feed and a secondary air feed. As will be discussed the secondary air feed is of a pressure less than the pressure of the primary air feed. The primary higher pressure air flow traverses and exits the gun through central tube carried within and extending slightly without the barrel at the exit end. The secondary lower pressure air flow traverses and exits the barrel of the powder gun as a flowing annular column of air which completely envelops the primary flow.

It has been found, by the incorporation of a secondary air flow, that significant improvement in operation is achieved. Firstly, noise, if the primary air flow is within the range of from about 50 to about 100 psi and the secondary air flow is within the range of from about 25 to about 50 psi is reduced to a tolerable level. A reduction of noise level has been achieved when employing a primary air flow of approximately twice the pressure of the secondary air flow. Particularly, the noise level at a 1 foot measured distance from the present gun when operating at preferred values of psi for the primary air flow and 40 psi for the secondary air flow produced a reading of 93 dbs. On the other hand the noise level reading observed at the same distance when operating with a powder gun having only a primary air flow of 95 psi was 106 dbs. The incorporation of the secondary flow produced a reduction in noise level by 13 dbs. at a 1 foot distance or over a ten-fold reduction in the noise level experienced.

Somewhat similar reductions in noise level are experienced at greater distances away from the pneumatic powder gun.

The reduction in noise level, achieved by the incorporation of the described secondary flow, is believed to result from a smaller differential between the pressure at the high pressure outlet and theosurrounding pressure of the secondary flow than would be the differential if the secondary flow were absent. Because of secondary flow of air the air exiting the primary pressure outlet is prevented to a great degree from breaking over the tip of the barrel and becomes somewhat entrained in the low pressure annular flow.

It has additionally been found that the pneumatic powder gun of the present invention provides a more even dispersion of powder over the gloves carried by the array of molds. Thus, while a high pressure flow is required and serves to carry the powder material over a larger area, the powder which is propelled through the pneumatic powder gun through entrainment by the secondary air source is carried by but never attains the velocity of flow of the primary air flow. Consequently, the powder is capable of following eddy currents within the hood 12 rather than following a generally downward path past each glove.

A conduit 60 positioned to be concentric with axis of the pneumatic powder gun provides a primary air flow line. The conduit projects slightly from one end of the barrel and at the other is fixed to a connector 62. The connector may be threadedly or in any convenient manner received and secured at one end of air inlet manifold 64. The manifold comprises an elongated member having a central bore 66 through which conduit 60 passes. The bore at the connector end is of a diameter at least equal to the outer diameter of conduit 60 while the bore at the other end is somewhat enlarged, within the region 68. The bore at both ends is outwardly beveled and threaded substantially along the beveled length.

A second connector 70 is likewise received by the manifold 64 within the region of the larger bore. High pressure air from a source (not shown) is communicated to the high pressure line by means of connector 62. Connector 70 serves the same purpose with respect to the lower pressure air flow.

A barrel 72 is threadedly received by the other end of the manifold 64. The barrel 72 is of elongated cylindrical form providing a central bore through which the secondary air flow from chamber 68 may pass. As is apparent the flow is annular around the conduit 60 and exits the barrel 72 in a similar annular flow pattern. Support structure (not shown) maintains the positioning of the barrel 72 relative to the conduit 60 at the end 74.

A further barrel comprising a powder feed barrel 76 is telescopically received by and secured to manifold 64. To this end the manifold at the end opposed from the connector 62 is annularly cut to provide shoulder 78. The powder manifold is slidingly received against the shoulder and secured, for example, by thumb screw 80. The powder barrel provides a chamber 82 throughout its length which surrounds the secondary air barrel. The neck 84 of funnel 28 is threadedly received by the powder barrel and permits powder material from the hopper 24 to enter the chamber 82.

The pneumatic powder gun includes an additional barrel 86 providing an elongated central bore surrounding at one end the barrel 72.. The barrel 86 is annularly cut at one end while the powder barrel is undercut in a manner to be complementary whereby the parts are received against shoulders 88 and 90. Securement may be achieved by means of a set screw 92. The end of barrel 86 is beveled to provide a smooth transition between the chamber 82 and the bore of barrel 86.

As with the barrel 72 the conduit 60 in like manner is stabilized and maintained in proper position in relation to the barrel 86.

In operation, a primary high pressure line is coupled to connector 62. High pressure air passes through the conduit 60 exiting at 102. A secondary lower pressure line 104 is coupled to connector 70. Lower pressure air follows a path which is defined by the chamber 68, barrel 72 and barrel 86, exiting the powder gun at 106 in an annular flow pattern.

As heretofore discussed, powder material dispensed from hopper 24 falls into the funnel 28. The powder falls through gravity and thereafter in addition to the force of gravity is drawn into the chamber 82 by the creation substantially of a vacuum or reduced pressure zone, relative to atmospheric pressure above the constriction of the funnel 28, within the chamber in the region below the outlet of neck 84 and extending to the location at which low pressure air exits conduit 72. This condition is created by the escape of the low pressure air flow from the conduit 72 into the larger uniform diameter barrel 86. By this condition the powder is pulled into the barrel 86 whereat it entrains with the low pressure or secondary air flow. The powder material tends to become further entrained by the high pressure primary air flow but never achieves its velocity. However, the primary flow serves to direct the flow of powder as well as to carry the powder throughout the area of the array.

Having described the invention, I claim:

1. A method for dispensing and spraying pulverulent material on a product to be coated thereby using a spray gun from which the material is sprayed comprising the step of developing a first high velocity flow in one direction, developing a second lower pressure flow surrounding the first flow in the same direction, while introducing pulverulent material to the second flow to become initially entrained with said second flow whereby part of said entrained material is thereafter transferred to the first flow downstream from the end of the gun apparatus. Amend the following claim:

2. Apparatus for spraying pulverulent material on a product in accordance with the method of claim 1, said apparatus comprising an elongated Ibarrel having a central bore throughout, first means closing said barrel at one end and providing a first fluid line within at least the length of said bore, said means adapted for communication with a source of fluid high pressure to develop said first high velocity flow therefrom, means providing a second fluid line throughout at least a portion of the length of said bore, connector means mounted in said barrel in fluid communication with said second fluid line, said connector adapted for communication with a second source of fluid under lower pressure to develop the said second flow therefrom, a chamber within said bore, and means for delivering said pulverulent material to said chamber whereupon because of pressure conditions created by movement of said second flow said material moves through said chamber, toward and into entrainment with said second flow upon exiting said second fluid line.

3. The apparatus of claim 2 wherein said first line provides a columnar fluid flow.

4. The apparatus of claim 2 wherein said first fluid line provides a columnar fluid flow and said second fluid line provides an annular fluid flow which envelops substantially said columnar fluid flow after exiting said first fluid line.

5. The apparatus of claim 2 wherein said first means includes a connector at said one barrel end and an elongated conduit, means to support said conduit within said bore and concentrically of said barrel.

6. The apparatus of claim 5 wherein said means providing a second fluid line includes a second conduit, and means to support said second conduit within said bore and in concentric relation to said elongated conduit thereby to form an annular space, said annular space defining said second fluid line.

7. The apparatus of claim 6 wherein said connector means mounted in said barrel is disposed between said second fluid line and said barrel end connector.

8. The apparatus of claim 6 wherein said second fluid line terminates within said bore and the velocity of said second fluid flow within said second fluid line is greater than the velocity of said second fluid flow without said second fluid line thereby to create a relative negative pressure condition within said chamber.

9. The apparatus of claim 2 wherein said chamber is isolated from said second fluid flow at the entrance to said second fluid line.

10. The method of applying powder to plastic gloves using a substantially closed chamber comprising the steps of a. providing a plurality of gloves;

b. moving the gloves into the chamber;

c. dispensing powder as the pulverulent material, in accordance with the method of claim 1, into the chamber, while d. maintaining the gloves in the chamber for a sufficient time to coat them with the dispensed powder. 

1. A method for dispensing and spraying pulverulent material on a product to be coated thereby using a spray gun from which the material is sprayed comprising the step of developing a first high velocity flow in one direction, developing a second lower pressure flow surrounding the first flow in the same direction, while introducing pulverulent material to the second flow to become initially entrained with said second flow whereby part of said entrained material is thereafter transferred to the first flow downstream from the end of the gun apparatus. Amend the following claim:
 2. Apparatus for spraying pulverulent material on a product in accordance with the method of claim 1, said apparatus comprising an elongated barrel having a central bore throughout, first means closing said barrel at one end and providing a first fluid line within at least the length of said bore, said means adapted for communication with a source of fluid high pressure to develop said first high velocity flow therefrom, means providing a second fluid line throughout at least a portion of the length of said bore, connector means mounted in said barrel in fluid communication with said second fluid line, said connector adapted for communication with a second source of fluid under lower pressure to develop the said second flow therefrom, a chamber within said bore, and means for delivering said pulverulent material to said chamber whereupon because of pressure conditions created by movement of said second flow said material moves through said chamber, toward and into entrainment with said second flow upon exiting said second fluid line.
 3. The apparatus of claim 2 wherein said first line provides a columnar fluid flow.
 4. The apparatus of claim 2 wherein said first fluid line provides a columnar fluid flow and said second fluid line provides an annular fluid flow which envelops substantially said columnar fluid flow after exiting said first fluid line.
 5. The apparatus of claim 2 wherein said first means includes a connector at said one barrel end and an elongated conduit, means to support said conduit within said bore and concentrically of said barrel.
 6. The apparatus of claim 5 wherein said means providing a second fluid line includes a second conduit, and means to support said second conduit within said bore and in concentric relation to said elongated conduit thereby to form an annular space, said annular space defining said second fluid line.
 7. The apparatus of claim 6 wherein said connector means mounted in said barrel is disposed between said second fluid line and said barrel end connector.
 8. The apparatus of claim 6 wherein said second fluid line terminates within said bore and the velocity of said second fluid flow within said second fluid line is greater than the velocity of said second fluid flow without said second fluid line thereby to create a relative negative pressure condition within said chamber.
 9. The apparatus of claim 2 wherein said chamber is isolated from said second fluid flow at the entrance to said second fluid line.
 10. The method of applying powder to plastic gloves using a substantially closed chamber comprising the steps of a. providing a plurality of gloves; b. moving the gloves into the chamber; c. dispensing powder as the pulverulent material, in accordance with the method of claim 1, into the chamber, while d. maintaining the gloves in the chamber for a sufficient tiMe to coat them with the dispensed powder. 